Anti-chatter switching device



Feb. 23, 1960 s. w. BROWN ET ANTI-CHATTER swmcnmc DEVICE 2 Sheets-Sheet 1 Filed March 4, 1957 INVENTORS.

ATTORNEY Feb. 23, 1960 BROWN 1: AL 2,926,229

ANTI-CHATTER SWITCHING DEVICE Filed March 4, 1957 2 Sheets-Sheet 2 INVENTORS.

SANFORD W. BROWN AUGUSTINO ALBANESE BY @i ATTORNEY United Sttes Patent 2,926,229 ANTI-CHATTER swrrcnnsr; DEVICE Sanford W. Brown, Norwalk, and Augustine Albanese,

Bellfiower, Califi, assiguors to North American Aviation, Inc.

Application March 4, 1957, Serial No. 643,663

* Claims. (Cl. 200-104) This invention relates to a switching device and more particularly to a switching device having contact elements particularly shaped to eliminate friction and chatter.

Where a switching device is to he used under conditions of extreme vibration, it is difficult to get operation without contact chatter (i.e. rapid opening and closing of the contacts with vibration). This problem becomes even more critical where the switch is to be operated under the vibration conditions encountered in a rapidly maneuvering high speed vehicle such as a missile. In such a situation, the switch may be subjected to accelerations in the neighborhood of 15 or more times the acceleration of gravity. Switches with the commonly known type of contacts all tend to chatter under such conditions. Such chatter causes malfunctioning of equipment, which is intolerable, especially where precision con trol is required.

The device of this invention provides a contact which will not chatter when subjected to accelerations well in excess of 15 times the acceleration of gravity. This end is achieved by the use of a freely rotatable ball contact mated with a companion contact surface. Further, the use of a freely rotatable ball as one of the contact surfaces achieves greater reliability over long periods of use because different parts of the ball contact are used as the contact surface on successive closings of the switch. This tends to minimize pitting and similar Wear on the ball contact surface.

In devices where a movable contact is held against a fixed contact by a coil spring, the electrical load is passed from a terminal on the fixed contact to the movable contact and thence through the spring to another terminal. This is often undesirable because most good coil springs are made of materials with relatively high electrical resistance. This results in a high resistance switch path with undesirable power losses and heat dissipation. Further, military specifications prohibit the use of coil springs inan electrical circuit. In one embodiment of this invention this problem is overcome by having both electrical load terminals on separate segments of the fixed contact. The movable contact is caused to bridge the two'to permit curent flow.

It is therefore an object of this invention to improve the construction and operation of switches.

It is a further object of this invention to eliminate switch contact chatter.

It is another object of this invention to remove the mounting of a movable switch element from the electrical circuit operated thereby.

It is a further object of this invention to provide a more reliable switch for use in continuous operation.

A still further object of this invention is to provide a switch which will not break contact when subjected to very high accelerations.

It is still another object of this invention to provide a switch which will perform reliably in a rapidly maneuvering vehicle such as a missile.

2,926,229 Patented Feb. 23, 1960 Other objects of this invention will become apparent from the following description taken in connection with the accompanying drawings in which- Fig. 1 is an elevation view of a first embodiment of the invention;

Fig. 2 is a plan view of a second embodiment of the invention;

Fig. 3 is an isometric drawing of a representative contact assembly which can be used in the embodiment of this inventionshown in Fig. 1; and

Fig. 4 is anisometric drawing of a contact assembly which can be used in the embodiment of the invention shown in Fig. 2.

Referring to Fig. 1 which shows an embodiment of the invention utilizing a single ball contact, contact arm 1 is pivotally supported at pivot point 2 by support 3. Ball contact 4 is held in ball support 5 by the constraining action of spring 6 pushing against the shaft 28 of the ball support with the ball held in recess 15 of the contact assembly 13 (see Fig. 3). Arm 1 is formed with a recess 40 which slidably receives spring 6 and shaft 28. As arm 1 and base support 3 are generally made of metal, if it is desired that ball contact 4 be electrically insulated from the arm, ball support 5 can be made of an insulating material or of a metal with its surface coated with an insulation such as, for example, anodizing (oxidation of the surface by chemical reaction) will provide. The materials of the arm, base, and ball support are not critical and can be any suitable electrically conductive or insulating material. It is essential, however, that ball contact 4 have a highly electrically conductive surface. The ball contact can be, for example, of copper or silver as the situation dictates, or any suitable metal plated with a highly conductive material. Contact assembly 13 is fixedly attached to base 3. If this base is made of electrically conductive material, the contact assembly should be insulated therefrom by a suitable electrical insulator, 41.

The switch illustrated in Fig. 1 is an electrical relay actuated by solenoid 8 which receives electrical power from current source 9 when switch 10 is closed. Spring 11 keeps the switch arm in the up position, i.e. constrained against stop 12 which is part of the base support 3, when the solenoid is not energized, as indicated. When the solenoid is actuated by closing switch 10, arm 1 is pulled down by magnetic action so that ball contact 4 shown by solid lines to be in contact with segments 13a and 13b of contact assembly 13 is brought into contact With segments 13c and 13d as indicated by the dotted lines. In such a magnetically operated device, it is essential that at least a portion of arm 1 proximate to solenoid 8 be fabricated of a magnetic material to assure that the arm is drawn down by magnetic action when switch 10 is closed.

While the device shown in Fig. 1 is magnetically actuated, such control means are not essential and any suitable means for moving arm 1 to alternatively electrically connect segment 13a with 13b or segment 13c with 13d can be used. Referring to Fig. 3, contact assembly 13 utilized in Fig. 1 is shown in detail. This assembly comprises four electrically conductive segments 13a, 13b, 13c, and 13d insulated from each other by separators 14a, 14b, and 140. Each contact assembly has an electrical terminal thereon, 43a, 43b, 43c, the terminal on 13d not being shown. The terminals are adapted to be attached to electrical circuits to be switched. Conductive segments 13a, 13b, 13c, and 13d should be made of a highly electrically conductive material such as copper, silver or any suitable material which has been plated with a highly electrically conductive material. Separators 14a, 14b, and may be made of any suitable electrically insulating material. The contact assembly has a toroidally shaped (i.e. curved both transversely and longitudinally) recess 15 which runs its entire length. This recess has a transverse radius of curvature (ina plane perpendicular to the direction of motion of the ball contact and arm assembly) substantially equal to the radius of ball contact 4 inorder to constrain translational motion of the ball to rotary motion about the pivot axis 2. The-longitudinal contact surface of the recess should have a radius of curvature (ina plane coincidental with the direction of motion of the ball contact and arm assembly) sub stantially equal to the distance between pivot 2 and the extreme end of ball contact 4 in order to provide uniform contact pressure between contact ball 4 and recess 15 throughout the pivotal motion of the arm 1. Under these conditions, ball contact 4 will fit snugly into the recess and will make good contact with the contact assembly throughout its pivotal path. The recess may be cylindrical (i.e. curved only transversely) in which case extension of spring 6 will maintain ball contact 4 in contact with the contact assembly as the arm pivots.

It can be seen that ball contact 4 will make firm contact between contact assembly segments 13a and 13b in one of its positions and between segments 13c and 13d in the other. Longitudinal accelerations with the ball contact in either position might cause the ball to ride up and down slightly within the toroidal recess 15 but should not cause it to break contact between the two segments. Similarly, transverse accelerations might cause the ball to roll within its recess but should not cause a contact break. The fact that the ball can rotate freely will alleviate friction between the contact assembly and the ball contact under conditions of extreme vibration. It thus can be seen that continuous contact can be maintained under even the most extreme conditions of vibra tion. It is to be further noted that as the ball contact rotates freely, different portions of the ball will probably be used for making contact on successive changing of switch position. Thus over a period of time, the entire surface of the ball contact can be utilized in making electrical connection thereby permitting longer life and greater reliability.

It can readily be seen that the device illustrated in Figs. 1 and 3 can be adapted to cover as many successive contact positions as application requirements may dictate by the addition of identical contact assembly segments and provision for additional contact arm positions. In addition, the arm itself can be utilized as one of the contacts and the signals to be switched fed between the arm and the contact assembly segments. In such a case, ball support and arm 1 should be electrically conductive. Arm 1 should further have a suitable electrical terminal attached thereto. The electrical signals would then be switched between the arm terminal and the terminals on the various segments of the assembly as desired.

- Referring to Fig. 2, an embodiment of this invention which is a four pole double throw switch is illustrated. Arm 16 has four identical integrally formed or rigidly connected sections 16a, 16b, 16c, 16d, and is fabricated of an electrically conductive material, and ball contacts 17a, 17b, 17c and 170! are essentially the same as that described for the first embodiment. These ball contacts are similarly spring constrained by springs 18 against cylindrical recesses 32 (see Fig. 4) in contact assemblies 19 and are held in ball supports 30 in each arm section. Fixed contact assemblies 19a, 19b, 19c, and 19d are similar in construction to that indicated in Fig. 3 except that each assembly requires only two segments 20a and 205 as indicated in Figs. 2 and 4. These two segments are electrically insulated from each other by separator 21. The contact assemblies can be fixedly attached to base support 47 and should be insulated therefrom if this base is fabricated of an electrically conductive material. In the position indicated by solid lines in Fig. 2, all the 20b segments of contact assemblies 19a, 19b, 19c, and 19d are connected together through arm 16. Solenoid 22 has been actuated by closing switch 23 and thereby applying a current from power source 24. Lever 25 which is fabricated of a magnetic material and fixedly mounted on arm 16 has been drawn toward solenoid 22 moving contact arm 16 to the position indicated in Fig. 2. As indicated by the dotted lines, spring 26 moves arm 16 to bring the ball contacts into contact with the respective 20:: segments of contact assemblies 19a, 19b, 19c, and 19d when solenoid 22 is de-energized. Lever 25 is held against stop 35 in this position. The arm 16 is pivotally mounted on base 4-7 at pivot point 50.

The second embodiment can also be readily modified to include additional ball contacts and contact assemblies as the application may demand; It, too, can be actuated by any suitable means, and the solenoid indicated in Fig. 2 is only one means suggested for changing switch position.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

We claim:

1. A switching device comprising a freely rotatable ball contact, a contact assembly having a plurality of electrically conductive segments, said segments being electrically insulated from each other, said contact assembly further having an elongated recess in one surface thereof extending longitudinally of said surface, said recess having a transverse radius of curvature substantially equal to the radius of said ball contact, a pivotally mounted contact arm supporting said ball contact within said recess in contact with said contact assembly, said one surface and said recess of said contact assembly having a longitudinal curvature with a radius substantially equal to the distance between said contact arm pivot and the end of said ball contact adjacent said contact assembly, the longitudinal centerline of said contact arm being normal to a tangent to said recessed surface of said contact assembly at the point of contact thereof with said ball contact, means for changing the position of said arm to bring said ball contact into contact with each of said segments of said contact assembly, individually, and means for rigidly holding said arm in the preselected contact positions.

2. The device recited in claim 1 wherein said switching device is an electrical relay and said means for changing the position of said ball contact is a solenoid.

3. A switching device comprising a spring constrained electrically conductive ball contact, a contact arm having two ends, said ball contact being rotatably mounted on one end of said arm, support means for said contact arm, the other end of said contact arm being pivotally mounted on said support means, a contact assembly having a plurality of electrically conductive segments, said segments being electrically insulated from each other, said contact assembly having a toroidal recess on one surface thereof, means for supporting said contact assem bly in contact relationship with said ball contact within said recess in said contact assembly, the longitudinal centerline of said contact assembly being normal to a tagent to the surface of said contact assembly at its point of contact with said ball contact, means for moving said contact arm between a plurality of predetermined positions, and means for rigidly holding said arm in each of said positions, said ball contact making electrical contact between two of said electrically conductive seg ments of said contact assembly in each of said arm positions.

4. A switching device comprising a spring restrained electrically conductive ball contact, a contact arm having two ends, said ball contact being rotatablymounted on said one end of said arm, support means for said con tact arm, the other end of said contact arm being pivotally mounted on said support means, a contact assembly having a plurality of electrically conductive segments, said segments being electrically insulated from each other, said contact assembly having a toroidal recess on one surface thereof with a transverse radius of curvature substantially equal to that of said ball contact and extending the entire length of said one surface, said contact assembly further having a longitudinal curvature on said one surface thereof with a radius substantially equal to the distance between said contact arm pivot and the end of said ball contact adjacent said contact assembly, means for supporting said contact assembly in contact relationship with said ball contact, said ball contact being within said recess in said contact assembly, the longitudinal centerline of said contact arm being normal to a tangent to the surface of said contact assembly at its point of contact with said ball contact, means for moving said contact arm between a plurality of predetermined positions, and means for rigidly holding said contact arm in each of said positions, said ball contact making electrical contact between two of said electrically conductive segments of said contact assembly in each of said arm positions.

5. In a switching device, a plurality of freely rotatable ball contacts, a plurality of contact assemblies, each of said assemblies having at least two electrically conductive segments insulated from each other, each of said contact assemblies further having an elongated recess in one surface thereof extending longitudinally of said surface, each of said recesses having a transverse radius of curvature substantially equal to the radius of its associated ball contact, a plurality of contact arms pivotally mounted for movement along the longitudinal axis of said contact assembly recesses, each of said contact arms supporting one of said ball contacts within a separate one of said contact assembly recesses, said recesses having a longitudinal radius of curvature substantially equal to the distances between said contact arm pivots and the ends of said ball contacts adjacent said contact assemblies, means for simultaneously changing the position of said arms to bring each of said ball contacts into contact with at least one of said segments of one of said contact assemblies successively, the longitudinal centerlines of each of said arms being normal to a tangent to the surface of a corresponding one of said contact assemblies at the point of contact with the associated ball contact, and means for rigidly holding said arms in each of the contact positions.

References Cited in the file of this patent UNITED STATES PATENTS 867,095 Bemus Sept. 24, 1907 1,449,347 Pearson Mar. 20, 1923 1,514,596 Adams Nov. 11, 1924 1,651,314 Beasley Nov. 29, 1927 1,781,927 Klein Nov. 18, 1930 1,949,694 Poli Mar. 6, 1934 2,201,882 Bryant et a1. May 21, .1940 2,825,768 Beck Mar. 4, 1958 

